The present invention relates in general to the field of optical irradiation, and more particularly, to an apparatus and method for custom spectral illumination using a computer controlled digital light processing micromirror or liquid crystal array and a linear variable filter to produce controlled spectra in time and space for use in, for example, microscopy, tissue engineering, image scanning and modifying cellular responses.
Without limiting the scope of the invention, its background is described in connection with known devices that are capable of directing light to specific locations using micromirror or digital light processor (DLP) arrays, as an example.
Heretofore, in this field, the analysis of biologically relevant samples has been accomplished using techniques that detect the presence of a marker or markers in known and unknown samples. To detect the presence of these markers, techniques such as, e.g., radiolabelling, fluorescence or enzymatic labeling, have been used to detect the presence or absence of binding between a component of the sample and a substrate or matrix on which the appropriate binding group or ligand has been immobilized. These methods, however, have been limited to the detection of samples and have not extended the use of technology to the modulation of cellular and other responses.
One such detection system is described in U.S. Pat. No. 5,744,305 is issued to Fodor, et al., in which a synthetic strategy for creating large scale chemical diversity in an array is described. Solid-phase chemistry, photolabile protecting groups and photolithography are used to obtain a light directed spatially-addressable parallel chemical synthesis. Using binary masking techniques, a reactor system is used that can be used to improve data handling and collection. The system described, however, uses a single light source and is limited to detection individual samples.
Another system and method of detection of samples is described in U.S. Pat. No. 5,424,186 issued to Fodor, et al. A method for synthesizing oligonucleotides on a solid substrate is described. The substrate used in the device described provides for the incorporation of semiconductor structures that are used to detect binding of samples to an array of ligands on the surface of the semiconductor. The system, however, is only useful for the detection of the material permanently attached to the surface of the chip. The system also requires an expensive customized reader to provide a limited output.
In parallel with the development of detection systems is the advent of Digital Light Processing, which has been pioneered by Texas Instruments as a way to achieve control of light using digital technology. Involving major innovations in micromachining and semiconductor electronics, Texas Instruments designed a single chip with mechanically actuated micromirrors, each 17 microns in size and with up to 2 million mirrors. Each DLP is capable of simultaneous control of each micromirror on a 20-microsecond time scale. The DLP is now the central component of many computer and video projection systems on the market. Unique to the DLP, is its ability to project a wide range of light spectra because the modulation component is, e.g., an aluminum mirror and not a liquid crystal.
It has been found that present apparatus and methods fail to meet the demands for a low cost, efficient, customizable method of creating spectrally controlled, small scale projection of light for use in the detection of variations in fluorescence as well as for light directed regulation of cellular functions. Present projection techniques require the use of multiple filters to create large scale projection systems that are not customizable for location, size, time variations, intensity and wavelength.
The present invention is based on the recognition that rapid, discrete wavelength changes are not possible due to the need to change filters at one or more locations in the light path. Present systems are incapable of being designed and used, at a reasonable cost to achieve the needed diversity for rapid changes in pattern and wavelength of the light projection. The present invention may be used in a wide variety of applications to provide one or more wavelengths of light in a controlled manner for use as a light source for microscopy, tissue engineering, two and three dimensional image scanning and even for modifying cellular responses.
More particularly, the present invention is an apparatus for generating a time and spatially dependent light spectrum that includes a light source positioned to direct a light output, a computer connected to, and controlling, the light source and a variable spectrum filter placed in the path of the light redirected by the light source. The variable spectrum filter passes one or more wavelengths of light that are redirected by the light source under the control of the computer. The light that enters the variable spectrum generator may be a beam, a line or even a light curtain. The light may be of one or more wavelengths, that is, simple or complex light. The light that passes the variable spectrum generator will be/of one or more wavelengths depending on the wavelength resolution of the variable spectrum generator and or the spatial width of the light directed toward the variable spectrum generator. After passing the variable spectrum generator the passed light may be used for microscopy, for imaging or even to generate a light curtain having defined wavelength characteristics in time and space. The light that passes the variable spectrum generator may even be a two dimensional light in which one axis provides for varying wavelengths and the other provides a position in space. A complex multiwavelength signal at this point may be detected by a CCD camera, deconvoluted by a computer or used for microscopy, tissue engineering, image scanning or modifying cellular responses.
A computer is connected to, and controls, a digital micromirror device (DMD) (aka digital light processor (DLP)) or generated by a liquid crystal display (LCD) that is placed in the path of light to be redirected by the micromirror or liquid crystal display. Light that strikes or is reflected by the DMD or selectively passed by a liquid crystal display (LCD) is then filtered using a Linear Variable Filter (LVF). In one embodiment, one LVF is placed before and one after the DMD to control the wavelength that strikes the DMD or LCD and that which is reflected by the DMD or generated by the LCD. In another embodiment, the LVF is used before the DMD or LCD. Light may be directed at the though lenses both before and after the light strikes, e.g., the DMD. Furthermore, light that is directed at the DMD or generated by the LCD may be of one or more wavelength and in a variety of shapes and sizes. Generally, the application of light to cells or tissue will determine the intensity and pattern of the light projected through the DMD. The light might strike the DMD as a single ray of light that rasterizes or scans through the DMD, strikes a portion or the entire surface area of the DMD, as a light line, spot, square, oval or in any shape necessary to achieve the necessary illumination of, e.g., cells or tissues.
A light source for use with the present invention in conjunction with a DMD is a lamp or laser, such as a UV light. In an alternative embodiment the light source may be, e.g., a xenon lamp, or a mercury lamp, a laser or a combination thereof or may even be generated by an LCD. The light produced by the light source may also be visible light. One advantage of using UV light is that it provides photons having the required high energy for biological or chemical reactions. UV light is also advantageous due to its wavelength providing high resolution. Lenses may be positioned between the light source and the computer controlled light modulator, which may be a micromirror or liquid crystal array or display, or between the micromirror and the target. An example of such a lens is a diffusion lens.
The light mediated stimulation, activation, inactivation or reaction may be, e.g., the dimerization of adjacent nucleotide bases to a third nucleic acid segment that is being used for, e.g., targeting gene expression. By targeting gene expression both a decrease and an increase in gene expression is encompassed.
Likewise, the light redirected by the micromirror may catalyze a chemical reaction, e.g., an amino acid addition reaction or the addition, removal or crosslinking of organic or inorganic molecules or compounds, small or large at the target site. For example, during the addition of a nucleic or an amino acid residue, the light may deprotect protecting groups of, e.g., phosphoamidite containing compounds. Light may also be responsible for the crosslinking or mono-, bi-, or multi-functional binding groups or compounds to attach molecules such as, fluorochromes, antibodies, carbohydrates, lectins, lipids, and the like, to the substrate surface or to molecules previously or concurrently attached to the substrate.
The present invention also includes a method of patterning light on a target by steps of: generating a light line, directing the light line into a variable spectrum generator, passing one or more wavelengths of light through the variable spectrum generator and illuminating a target with the one or more wavelengths of light passed through the variable spectrum generator. The target can also be physically moved relative to the light being directed to it.
The method of the present invention may further include the step of controlling, using a computer, the micromirror, which may be a light mirror array such as, e.g., a Texas Instruments Digital Light Processor. The illuminating light beam may be a UV, or other light source that is capable of, e.g., catalyzing a chemical reaction or causing a change in the state of a cell. By xe2x80x9cchanging the state of a cellxe2x80x9d it is meant that the cell undergoes a change that causes it to, e.g., divide, stop dividing, activate cellular functions such as the formation of lysozomes, secretion of proteins, hormones and the like. The present method may also be used for the in situ removal of cells by providing a light at an intensity sufficient to eliminate cellular functions, as will be known to those of skill in the art of photochemistry.
The method of the present invention may further include the step of, identifying a patient having a target site in need of light treatment and directing the light beam at the target site of the patient. The method may also include the steps of positioning the target site on or within a patient, flooding the target site a light catalyzable reaction chemical, such as a nucleotide or amino acid residue having, e.g., photoreactive side-groups, and exposing the chemicals reagents to light. The light catalyzable reaction chemical is activated and a reaction synthesis or decomposition is caused by light at the location where the micromirror redirects light on the target site, but not where the micromirror does not redirect light. The present invention may be used, e.g., in xe2x80x9cstepperxe2x80x9d or xe2x80x9crasterizerxe2x80x9d fashion, wherein the micromirror is directed at a portion of the target, that portion of the target exposed to light from the micromirror, and then xe2x80x9cstepperxe2x80x9d or xe2x80x9crasterizerxe2x80x9d on to a different portion. The new portion of the target exposed may be, e.g., overlapping or adjacent to the first portion.
The present invention may even be used as a general light source when an application calls for a light source that generates a controlled light spectra. The one or more spectra may be controlled in either time, space or both. In fact, the shape, wavelength, location and timing of the light may be controlled using the present invention. As a general light source the apparatus, system and method disclosed herein may be used for three dimensional scanning and for fluorescence and general light microscopy.
The timing, location, intensity, shape and wavelength of light may also be used to control the location and growth of cells in tissue engineering application, for example, to control the shape and location of growth of particular cells within a three-dimensional matrix. Furthermore, the timing, location, intensity, shape, timing and frequency of pulsing and wavelength of light may also be used to cause the regulation of cellular function. By regulation of cellular functions it is meant that cells may be caused to apoptose, grow, divide, secrete or cease secretion of cytokines and other chemical messengers and mediators, spread, adhere or de-adhere and the like.